21013925 has 6 divisors (see below), whose sum is σ = 26057298. Its totient is φ = 16811120.

The previous prime is 21013907. The next prime is 21013931. The reversal of 21013925 is 52931012.

It can be written as a sum of positive squares in 3 ways, for example, as 1943236 + 19070689 = 1394^2 + 4367^2 .

It is not a de Polignac number, because 21013925 - 2¹⁴ = 20997541 is a prime.

It is a Duffinian number.

It is a zygodrome in base 4.

It is a self number, because there is not a number n which added to its sum of digits gives 21013925.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 420254 + ... + 420303.

It is an arithmetic number, because the mean of its divisors is an integer number (4342883).

Almost surely, 2^21013925 is an apocalyptic number.

21013925 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21013925 is a deficient number, since it is larger than the sum of its proper divisors (5043373).

21013925 is an equidigital number, since it uses as much as digits as its factorization.

21013925 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 840567 (or 840562 counting only the distinct ones).

The product of its (nonzero) digits is 540, while the sum is 23.

The square root of 21013925 is about 4584.0947852330. The cubic root of 21013925 is about 275.9533851471.

Adding to 21013925 its reverse (52931012), we get a palindrome (73944937).

The spelling of 21013925 in words is "twenty-one million, thirteen thousand, nine hundred twenty-five".